Lotus Temple
This temple was built in 1980 and is the center of the Baha'i religion, a kind of philosophy based on respect and communication between various religions. Visiting is free, but it's strictly regulated (no shoes inside, only a few people in the temple at a time, and no noise). It's basically a guided visit since a person (who invariably reminds you of the rules) tells a little history of the religion and temple, before inviting you go to meditate. The entire tour takes around 30 minutes and of course you can stay longer to explore the gardens or meditate.